The evidence, described as "shocking" and "bizarre", was heard in the ACT Supreme Court on Tuesday as Nona pleaded not guilty to two counts of having sex with a child and two counts of an act of indecency in the presence of children.

Crown prosecutor Margaret Jones said Nona, 41, had sex with the girl in her home in February 1996 and again in April, causing her to become pregnant.

But Nona told the jury he never had sex with the girl, who he met while visiting a house known for hosting two- to three-day parties, with heavy drinking.

In his closing submission, Nona's barrister Shane Gill said hospital records showed the girl said she had spoken to her deceased grandmother, who allegedly visited her to protect her from evil spirits.

"It doesn't get much weirder than that," he told the jury. "Something incredibly weird was going on inside her head."

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Mr Gill said the girl had had been sexualised from a young age and developed a crush on Nona, once saying that she loved him.

On Monday, Nona told the court from the witness stand the girl had tried to kiss him once in the lounge of her home but he had pushed her away when she got close.

"It felt like she had a crush on me," he said.

Nona told the court the girl would hug him and sometimes he felt she was hanging on too long.

Nona also said the girl confessed to him once of having sex with him while he was passed out at her house after two days of binge drinking without food.

He said after waking, the girl approached him when they were alone and said: "I want to tell you something but you're not allowed to tell mum – I had sex with you last night."

Nona told the court his body turned cold and he wanted to leave the house immediately and asked her: "Why did you do that? You're going to get me into big trouble."

But Ms Jones said the jury should dismiss this confession as a lie, because it would have required a young girl to undress a grown man, have sex with him without his knowledge, and then sneak away.

In her closing submission, she told the jury this was not a case of a young girl developing a crush on an older man, but a sad case of the accused taking advantage of a vulnerable little girl.

The girl's pregnancy was not discovered until police were called to the house for an unrelated matter and her pregnancy was terminated 22 weeks after conception.

Ms Jones said the girl was too scared to tell her mother about her pregnancy and that she was trying to protect a man she had an "abnormal attachment" to.

Nona, who is from Badu Island about 60km north of Thursday Island, is also accused of committing acts of indecency in front of two children, aged 13 and 14 at the time.

The incidents are said to have happened while Nona was studying fine art at the Australian National University.

The Crown alleges the offences happened when the two children were in the backyard of a property and Nona knocked on a bedroom window to get their attention and then held his exposed penis in his hand.

The complainant told the court Nona was allegedly "playing with his penis as if it were a joke" and was "looking right at us".

Nona denied doing so.

Chief Justice Helen Murrel is expected to give jurors final directions and send them to begin deliberating on Wednesday.